I have but prefer newsprint.

I used to think I was saving money and time using plain copy paper, but I always ended up tearing the stitching out when removing paper, especially if I used Aurifil thread. I bought myself a package of Carol Doak's foundation paper and have been happy as can be ever since. It tears out easily and the package I bought has lasted forever. Well worth the pennies it cost!

I love the accuracy of using paper piecing. I use printer paper that is printed on one side rather than throwing it away. I don't use it for very small pieces, it is harder to remove.

I use newspaper weight paper. I bought a package on Amazon for less than 10.00. I think it will last forever and it is thin enough that it tears easily.

I use it too and other than being a bit tough to remove it works very well for me and it is always on hand.

I have used regular copy paper in a pinch. I find it harder to remove and it sometimes pulls my stitches out. I do like vellum the best but it can get pricey. I have used the cheap drawing paper tablets made for kids. I get it at the dollar store. It is an off white color, like newsprint. Depending on what tablet you find sometimes I have to trim it to fit in the copier. I keep my old rotary blades just for things like this.

I agree with SewingSuz. I use the thinnest, cheapest typing paper I can find.

I used to use it until I found newsprint paper on Amazon that is less expensive, tears away easier.

I find copy paper a bit too heavy for PP. I use newsprint that I purchase from the dollar store that comes in pads. It tears off really easily. Newsprint pads are much cheaper than copy paper.

I've practiced both with copy paper and newsprint.
With very small stitch length, they both tear pretty easy (newsprint is slightly easier).
However, the newsprint is way cheaper.
Also, don't forget to use up your old telephone book pages for paper piecing.